Bilge float switch switches, but not enough...

CaptainBob

CaptainBob

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My bilge float switch (rule-a-matic) switches on the pump when I flood the bilge, but doesn't give enough power to the pump for it to do anything. If I switch on the pump manually, bypassing the float switch, it works fine.

If I short out the wires going to the float switch, the pump works fine.

I measured the open and close circuit resistance in the float switch and it's 400 k Ohm open circuit and 360 Ohms closed circuit.

Seems like quite a large resistance but I'd not have thought that would be enough to stop the pump from operating. Batts were on charge at time of testing.

Am I missing something else? Anyone know the design resistance of a rule-a-matic float switch?
 
CaptainBob said:
My bilge float switch (rule-a-matic) switches on the pump when I flood the bilge, but doesn't give enough power to the pump for it to do anything. If I switch on the pump manually, bypassing the float switch, it works fine.

If I short out the wires going to the float switch, the pump works fine.

I measured the open and close circuit resistance in the float switch and it's 400 k Ohm open circuit and 360 Ohms closed circuit.

Seems like quite a large resistance but I'd not have thought that would be enough to stop the pump from operating. Batts were on charge at time of testing.

Am I missing something else? Anyone know the design resistance of a rule-a-matic float switch?
Click to expand...


Id expect a float switch to have no resistance when closed. At 12 volts the max current that will flow through 360 ohms is only 33 mA.
You pump will take a lot more than that. I am surprised it turns at all

A quick google suggests its just a float operated mercury tilt switch
 
Last edited:
CaptainBob said:
My bilge float switch (rule-a-matic) switches on the pump when I flood the bilge, but doesn't give enough power to the pump for it to do anything. If I switch on the pump manually, bypassing the float switch, it works fine.

If I short out the wires going to the float switch, the pump works fine.

I measured the open and close circuit resistance in the float switch and it's 400 k Ohm open circuit and 360 Ohms closed circuit.

Seems like quite a large resistance but I'd not have thought that would be enough to stop the pump from operating. Batts were on charge at time of testing.

Am I missing something else? Anyone know the design resistance of a rule-a-matic float switch?
Click to expand...

buy a solid state switch from forumite salty john
 
You might find it is a reed switch which will interrupt only milliamps. If so, fit a buffer relay with a reversed biased diode across it (to absorb the inductive kick). But it is probably burnt out with 360 ohms resistance.
 
Captn your resistance probably due to water/ dirt ingress . The switch loses watertight integrety over the years . Throw away and fit new . I'v had the symptons before and renewing solved it .

On wooden boats with yukky bilges was prudent to mount the switch up from the bilge and have it actuated by a "lump"polystyrene in a piece of plastic waste pipe. If you see what I mean .

Ps visited Maplins yesterday. Just got to sort which conn does what and I'm away.Cheers !!
 
CaptainBob said:
My bilge float switch (rule-a-matic) switches on the pump when I flood the bilge, but doesn't give enough power to the pump for it to do anything. If I switch on the pump manually, bypassing the float switch, it works fine.

If I short out the wires going to the float switch, the pump works fine.

I measured the open and close circuit resistance in the float switch and it's 400 k Ohm open circuit and 360 Ohms closed circuit.

Seems like quite a large resistance but I'd not have thought that would be enough to stop the pump from operating. Batts were on charge at time of testing.

Am I missing something else? Anyone know the design resistance of a rule-a-matic float switch?
Click to expand...
Open circuit should be more than you have, and closed circuit MUCH less - almost zero. New switch time.
 
Cheers for all the replies. I'd done the maths and got the wrong answer - I was using 0.36 for resistance instead of 360. Glad it's as simple as that. Thank you!

Clyst - nice one - hope I recommended the right relay; given my electrical skills performance in this thread!
 
Thanks for the endorsement but we no longer stock the Bilge Mate.
It's a good switch but the company that supply it, a company based in Florida, have no idea about communications and customer service so we dropped the product a year or so ago.
 
One on my pending electronics projects is a device that does away with the float switch, based on a similar device that I read about somewhere. It works as follows:

Run the bilge pump, if load current below threshold, turn off, sleep for 30 minutes.
Otherwise keep running until current drops, sleep for 5 minutes.
 
nigelmercier said:
One on my pending electronics projects is a device that does away with the float switch, based on a similar device that I read about somewhere. It works as follows:

Run the bilge pump, if load current below threshold, turn off, sleep for 30 minutes.
Otherwise keep running until current drops, sleep for 5 minutes.
Click to expand...

Just installed a Rule 500 automatice bilge pump yesterday, that is exactly how it works. It has a quick pump for a second evey 2.5 minutes. If there is water, it pumps till the resistance on the impellor drops, then it stops. It also has another lead for overriding if neccessary. No more float switch needed, just have to get used to the "gloop" every 2.5 minutes. Oh, also remember to switch it off if sleeping onboard, then on again in the morning!
 
nigelmercier said:
One on my pending electronics projects is a device that does away with the float switch, based on a similar device that I read about somewhere. It works as follows:

Run the bilge pump, if load current below threshold, turn off, sleep for 30 minutes.
Otherwise keep running until current drops, sleep for 5 minutes.
Click to expand...

Late to the party! If you want I have the code that does this and more using an MBED board. Supervise an existing float switch and take over if it fails, test pump every 24 hours, send SMS message to phone if it's failed. Monitor pump number of runs and total time run. Test pump for overload/blocked impeller, blocked exit hose ( all can be quite reliably read from stator current! )

With the extra IO on the board I use I get Barometric pressure , temperature and Humidity. Shore power monitor and 2 battery voltage monitors. An alarm montoring contact and 2 output ports that can be used as a dehumidifier control and frost heater or just as remote controlled outputs.

All the statii etc are reported via SMS on a programmable schedule and on 'alarm' conditions like shore power disconnected. Engine room too cold, bilge pump switch failed or bilge pump run for n minutes. perameters can be set via SMS.

A proper YAPP!
 
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